The present studies and those completed during the current funding period represent the first systematic investigation of factors involved in the regulation of fat intake and fat preference in obese and lean individuals. Despite advice to reduce fat intake because of its role in obesity, cardiovascular disease and cancer, people find this difficult because palatability is a major determinant of food selection, and fat can improve the flavor, odor, and texture of foods. To maintain "fatty" flavor and palatability while reducing fat content, a number of fat substitutes and fat mimetics have been developed. These products provide a unique tool for dissociating sensory and cognitive controls of fat ingestion from postingestive physiological controls. Our approach is to use rigorous laboratory-based procedures to isolate and define variables that affect human caloric and macronutrient intake. Specifically, we will determine in Experiment 1 how cognitive information (from labels indicating the fat content) and energy content interact to affect hunger, satiety and food intake when there is a dissociation between these cues. Although such dissociations are common with many of the new reduced-fat foods (i.e. a low-fat label on a calorically-dense food), there are no data as to their effects on eating behavior. In Experiment 2 we will test the hypothesis that addition of a fat substitute to a low-fat food will affect learning about the energy content of that food as the food is eaten repeatedly. The key question is whether subjects will learn that fatty tasting low-fat foods do not satisfy hunger, and if such learning occurs, will they either stop liking these foods, eat more of them to obtain additional energy, or eat more of other foods, including those high in fat. Finally, in Experiment 3, we will determine whether preference for fat can be reduced through long-term fat restriction, and whether preserving fatty flavor through the use of fat mimetics interferes with this change. In all studies we will be comparing the responses of obese and lean individuals to test the predictions that obesity is associated with: 1) poor regulation of intake of dietary fat; 2) an enhanced preference for fat which is resistant to, change; and 3) relatively greater reliance on cognitive compared to physiological influences. These studies will provide important new information on the regulation of dietary fat intake and preference, forming the foundation for more mechanistic analyses to follow. In addition, these studies will suggest appropriate strategies for increasing compliance to low-fat diets in lean and obese individuals.